Polymerization process with a complex metal hydride-aluminum trialkyl-titanium halide catalyst



PGLYMEREZATEON PRQQESS WETH A QOMPLEX METAL HYDRIiDEALiJh llNiHi/i TRlALKYL-Tl- TANIUM HALEBEE. QATALYST lohn R. Lovett, Metnchen, and Joseph M. Kelley, 51's., Cranjrord, N..l., assignors to Essa Research and Em gineering Qompany, a corporation of Delaware No Drawing. Filed Get. 20, USS, Ser. No. 768,023

6 Claims. Cl. 260-93.?)

This invention relates to an improved process for the low-pressure polymerization of olefins and more particularly to an improved polymerization process which results in an elevation in the melt index of the polymer products.

The low-pressure polymerization of alpha olefins with catalyst systems made up of reducible transition metal compounds and reducing metal containing compounds is Well known to the art; see e.g. Belgian Patent 533,362, Chemical and Engineering News, April 8, 1957, pages 12 through 16, and Petroleum Refiner, December 1956, pages 191 to 196.

It is known for example that ethylene can be polymerized using a catalyst system consisting of a reducible transition metal compound reduced with a metal hydride of a group ill metal, such as aluminum. These catalyst systems, however, do not produce polymers of controlled melt index.

It has now surprisingly been found that when a catalyst system containing at least three necessary components, namely (a) a reducible transition metal compound, (b) an organo-metallic compound, and (c) a mixed group l-group Ill metal hydride or aluminum hydride is used to polymerize alpha olefins, accurate control of polymer melt index and polymer molecular weight are obtained.

Reducible transition metal compounds which can be used as a catalyst component include inorganic compounds such as the halides, oxyhalides, complex halides, oxides, hydroxides, and organic compounds such as alcoholates, acetates, benzoates, and acetylacetonates oi the transition metals of the IV, V, VI, VII and VIII periods of the periodic system, and iron and copper, e.g. titanium, zirconium, hafnium, thorium, uranium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten, and manganese. The metal halides, particu larly the chlorides, are generally preferred. Titanium and zirconium are the preferred metal components since they are the most active of these metals.

Preformed partially reduced transition metal compounds can also be used as the transition metal compound, and in fact are preferred in the present invention. These catalyst components are partially reduced heavy transition metal compounds or partially reduced heavy transition metal compounds cocrystallized with a grou II or III metal compound such as halides, e.g. aluminum chloride, boron trichloride, zinc chloride, and the like. The partially reduced heavy transition metal compounds include inorganic compounds such as the halides, oxyhalides, complex halides, oxides and hydroxides, and organic compounds such as alcoholates, acetates, en-

zcates, and acetonates of the transition metals of the IV,

V, VI, VII and VIII groups of the periodic system, and iron and copper e.g. titanium, zirconium, hafnium, thorium, uranium, vanadium, niobium, tantalum, chromium, molybdenum, tungsten and manganese. The metal halides, particularly the chlorides, are generally pre ferred; especially crystalline titanium trichloride. Crystalline titanium trichloride cocrystallized with aluminum chloride is even more preferred. When the catalyst is a partially reduced heavy transition metal compound cocrystallized with a group I or ill metal compound, the catalyst contains from 0.05 to 1.0, preferably 0.1 to 0.5 mole of the group H or Ill metal compound per mole of partially reduced heavy transition metal compound. The partially reduced heavy transition metal compounds can be prepared by any procedure known to the art and the preparation of these compounds is not Within the scope of the invention. However, some of the methods known for preparing the preferred preformed catalyst components, i.e. crystalline titanium trichloride and crystalline titanium trichloride cocrystallized with aluminum chloride are summarized below.

(1) Reduction of titanium tetrachloride with aluminum power in xylene at IOU-175 C. at atmospheric pressure.

-(2) Metal reduction or" titanium tetrachloride with either aluminum powder, titanium powder, or mixtures of aluminum and titanium powder in the absence of solvent at elevated temperatures.

(3) Hydrogen reduction of titanium tetrachloride at temperatures above about 650 C.

(4) Reduction of titanium tetrachloride with metal alkyls, AlEt in particular, in an inert diluent above about C.

(5) Heating a mixture of titanium tetrachloride and an aluminum alkyl after the formation of a brown precipitate at a temperature above about 70 C. in the presence of an inert diluent.

(6) Reducing titanium tetrachloride with an aluminum trialkyl by carrying out the reduction in temperature graded stages in an inert diluent and with an aluminum trialkyl/Ticl mole ratio of about 0.3/1.

(7) Heat reducing titanium tetrachloride at temperatures above about 1000 C.

num, tripropyl aluminum, triethyl aluminum, dialkyl aluminum halides such as diethyl aluminum halides and dimethyl aluminum halides, and methyl and ethyl aluminum halides. Organo-aluminum compounds with two hydrocarbon radicals or at least one hydrocarbon radical and one hydrogen and containing an electron attracting group such as an alkoxy, halogen, and organic nitrogen can be used. Mixtures of the above organo-metallic compounds can also be used such as mixtures containing ethyl aluminum dichloride and triethyl aluminum. The organo-aluminum compounds, especially trialkyl aluminum and dialkyl aluminum halide are preferred. All of the above compounds and the methods for their preparation are Well-known to the art.

The third component oil the catalyst system is a mixed group I-group Ill metal hydride such as LiA1H NaAlH NaBH and the like or All-l Additionally, mixtures of two or more mixed metal hydrides can be used such as a mixture of LiAlli and NaAll-l Also mixtures of Ali-I and one or more mixed metal hydrides can be used. l-lenceforth, when the term mixed metal hydride is used, it is to be understood to mean one or more of the above compounds, i.e. one or more of AlH LiaAll-L NaAlH NaBH and the like.

The catalyst system of the invention is prepared by first mixing the reducible transistion metal compound and the organo-metallic compound in an inert hydrocarbon diluent at a temperature of from about 20 to C. and thereafter adding to the resulting mixture a dispersion of the mixed metal hydride in an inert hydrocarbon diluent. Alternatively, the dispersion of the mixed metal hydride can be added to the polymerization reactortogether with or separately from the mixture of reducible transition metal compound and organo-metallic compound prior to the polymerization reaction. Also a portion of the mixed metal hydride can be added to the mixture of reducible transition metal compound and organs-metallic compound and a single or multiple increments thereafiter added to the polymerization reactor during the polymerization reaction. The mixture of reducible transition metal compound and organo-rnetallic compound contains about 0.5 to 3.0 moles, preferably 1.0 to 2.0 moles of organo-metallic compound per mole of reducible transition metal compound. The total quantities of these two components are mixed together either with or without pretreatment, or a staged reduction pretreat technique can be used, i.e. by adding timed increments of the organo-metallic compound to the total quantity of reducible heavy transition metal compound. From 0.1 to 3.0 moles, preferably 1.5 to 2.5 moles of the mixed metal hydride is used per mole of the organo-metallic compound, depending on the effect of the specific hydride chosen on reaction rate and polymer molecular weight.

The inert diluents that are employed for forming the mixed metal hydride dispersion, for forming the mixture of reducible transition metal compound and organometallic compound, and for carrying out the polymerization reaction in the present process are aliphatic and aromatic hydrocarbons. Examples of usefiul aliphatic hydrocarbon diluents are n-hexane, n-heptane and n-decane. The aromatic hydrocarbons are the preferred diluents for use with the preformed catalysts, which are the preferred catalysts for the present process. Aromatic diluents such as benzene, toluene, and the xylenes can be used. The inert diluents used herein should be substantially free of catalyst poisons such as oxygen, carbon monoxide, sulfur and water. The diluent used to form the mixed metal hydride dispersion can be the same or different from the diluent used to prepare the catalyst which in turn can be the same or difierent from the diluent used in the polymerization reaction. 1

The alpha olefins polymerized by the novel catalysts of the invention are aliphatic alpha olefins having from 2 to 20 carbon atoms, and which can be either straight or branched chain, e.g. ethylene, propylene, butane-1, pentene-l, 3-methylbutene-1, and the like. C to C alpha olefins are preferred herein since they form crystalline plastics.

The polymerization reaction is carried out by contacting the olefins to be polymerized with the catalyst system ofi the invention in an inert hydrocarbon diluent at a temperature of from 40 to 125 (3., preferably 70 to 115 C. and at pressures ranging from about to 150 p.s.i.g., in batch or continuous operation. The polymer product concentration in the polymerization reaction mixtures is preferably kept between about 2 and 25 wt. percent based on the total contents present so as to provide for easy handling of the polymerized mixture. When the desired degree of polymerization has been obtained, a 1 to 3 stoichiornetric equivalents of a chelating agent such as acetylacetone or diacetone alcohol per mole of total catalyst is added to the reaction mixture to dissolve and deactivate the catalyst. Thereafter a C to C alkanol such as methyl alcohol, isopropyl alcohol, or n-butyl alcohol is added to precipitate the polymer product from solution. Alternatively, the chelating agent and alkanol can be added together. The polymer product is then filtered and can be further washed with an alcohol or an acid such as hydrochloric acid and dried, compacted and packaged.

The polyolefins produced in accordance with the procass of the invention have melt indexes of from 1 to 20 at 250 C.

EXAMPLE I 0.46 g. of TiCl -033AlCl was added from a dropping tunnel to cc. of xylene containing 4.68 cc. of a one molar solution of AlEt in xylene. To this solution was added 0.0425 gram of LiAlH The resulting mixture was then added to 900 cc. of xylene which had been presaturated with propylene gas at 65 C. The temperature of this mixture was then raised to 80 C. and the polymerization reaction carried out for one hour at this temperature. Thereafter 500 cc. of methanol containing 1.5 gm. of acetylacetone was added to chelate the catalyst and to precipitate the polymer product. The polymer product was then filtered, washed with methanol and dried. 104.1 gm. of polypropylene product were obtained. The details of the catalyst preparation in the polymerization reaction together with the properties of the polypropylene product obtained are given in Table 1.

EXAMPLE H The catalyst preparation and polymerization reaction were carried out according to Example I except that 0.25 gm. of. LiAll-I were used. The details are given in Table 1.

EXAMPLE III The catalyst preparation and polymerization reaction are carried out according to the process of Example I except that no LrAll-L, was added. The details of this run are given in Table I for comparison purposes.

Table I BATCH ATMOSPHERIC PRESSURE POLYMERIZATIONS Ex. 1 Ex. II Ex. III

Catalyst:

Tick-0.33 A1013, g 0. 16 0. 46 0. t6 AlEta, cc. of 1 molar s01 4. 68 4. 68 4.68 LiAlI-It 0. 0425 0.25 0 Polymerization conditions:

Propylene, l./min 1. 5 1. 5 2. 0 Total reaction time, min.-. 60 60 60 Catalyst, cone, g./l..... 1 1 1 Drluent xylene xylene xylene Temperature, 0 80 8O 80 Reaction rate, w./hr./\v 104.1 36. 9 114. 9 Results:

Amorphous polymer, percent 6. 2 6.6 4 7 Insoluble polymer, g.-

W ei t, g 97. 7 34. 5 109. 6 Melt index:

@190 C 0.10 0. 9 0.11 2m 0 0. 79 as 0.75 Intrinsic V1s., DL/g..- 2. 54 1.85 2.65 Harris Molecular Wt. 10- Tensile strength, p.s.i 5, 060 5, 585 '4, 600 Elongation, percent 40 50 It can be seen from the above table that a marked increase in the melt index of polypropylene was obtained using the catalyst system of the invention (Example II). This increase in melt index which is reflected also in molecular weight control renders the processing of poly alpha olefins very much easier, particularly with respect to the ease of extrusion which is important when the polymers of the invention are used in such applications as molded articles, e.g. bottles, pipes, hoses and the like. Additionally, it should be noted that the tensile strength of the polymer of Example 11 is about 1000 p.s.i. higher than the tensile strength of the polymer of Example III prepared in the absence of LiA1H This increase in tensile strength is an additional advantage of the invention and it renders the polymer of the invention useful in applications where high tensile strengths are desirable, such as in plastic pipes.

The invention is not limited to the examples which are given for illustration purposes only. Also modifications of the process will occur to those skilled in the art without departing from the spirit and scope of the invention.

What is claimed is:

1. The process for the polymerization of an alpha olefin by a low pressure polymerization process comprising the steps of polymerizing an alpha olefin having from 2 to 5 carbon atoms in an inert hydrocarbon diluent with a catalyst system consisting essentially of (l) a halide of titanium cocrystallized with an aluminum halide, (2) from 0.5 to 3.0 moles of a trialkyl aluminum compound per mole of titanium halide, (3) about 1.5 to 2.5 moles of a group I and a group HI mixed metal hydride per mole of trialkyl aluminum compound; and isolating the resulting alpha olefin polymers.

2. The process of claim 1 wherein catalyst component (3) is in the form of a dispersion.

3. The process of claim 1 wherein said titanium halide is crystalline TiC1 cocrystallized with aluminum chloride.

4. The process of claim 1 wherein component (3) is LiAlHi,

5. The process of claim 1 wherein the alpha olefin is ropylene 6 6. The process of claim 1 wherein component (1) is crystalline TiCl cocrystallized with aluminum chloride, and component (2) is triethyl aluminum.

5 References Cited in the file of this patent UNITED STATES PATENTS 2,827,447 Nowlin et a1 Mar. 18, 1958 2,846,427 Findlay Aug. 5, 1958 2,886,561 Reynolds et al May 12, 1959 2,914,515 Stuart Nov. 24, 1959 3,010,787 Tornqvist Nov. 28, 1961 FOREIGN PATENTS 15 543,913 Belgium June 23, 1956 OTHER REFERENCES RufI" et al.: Zeitschrift fiir anorganische Chemie, February 23, =1923, vol. 128, pp. 81-95, page 84 only 20 needed. 

1. THE PROCESS FOR THE POLYMERIZATION OF AN ALPHA OLEFIN BY A LOW PRESSURE POLYMERIZATION PROCESS COMPRISING THE STEPS OF POLYMERIZING AN OLPHA OLEFIN HAVING FROM 2 TO 5 CARBON ATOMS IN AN INERT HYDROCARBON DILUENT WITH A CATALYST SYSTEM CONSISTING ESSENTIALLY OF (1) A HALIDE OF TITANIUM COCRYSTALLIZED WITH AN ALUMINUM HALIDE, (2) FROM 0.5 TO 3.0 MOLES OF A TRIALKYL ALUMINUM COMPOUND PER MOLE OF TITANIUM HALIDE, (3) ABOUT 1.5 TO 2.5 MOLES OF A GROUP I AND A GROUP III MIXED METAL HYDRIDE PER MOLE OF TRIALKYL ALUMINUM COMPOUND; AND ISOLATING THE RESULTING ALPHA OLEFIN POLYMERS. 